For what I do:
Chrome Canary, or Dev if you want 99.9% stable releases. Even though canary has been perfect for me.
ThunderBird
Transmission
VLC
VMWare Fusion
Office
The ones listed below are MUST HAVES for everyone, regardless of what you use your computer for:
Better Touch Tool
Growl
iStat Menu
HyperDock
CoolBook
TotalFinder
SMC Fan Control(just because you can have fan speed and CPU temp listed in 2 lines in the menu bar)
yikes! i only have istat from your "must have" list, and i could happily do without it. i have been using my computer for a couple of months now with no problems. i think these are not "must haves"
what's essential and what's not depends entirely on what you use your computer for. here's my list. i'm a grad student/researcher/lecturer. i'd call it my top eight, but i realize they might not make it into some other people's lists at all. i use more stuff, of course, but these are the ones that are open every day.
1. chrome (browsing)
2. microsoft office (work)
3. adobe acrobat pro (pdf manipulation--good if you are going paperless, and inexpensive if you can get academic discount)
4. bookends (bibliographic app)
5. evernote (everything goes in here--good if you are going paperless, and great if you sync across devices)
6. houdahspot (good for searching)
7. sugarsync (online backup)
8. voodoopad (personal wiki)